A fully tested shot may not be ready until year's end, WHO says
MONDAY, July 13 (HealthDay News) -- A fully tested swine flu vaccine may not be available until the end of the year, a vaccine expert at the World Health Organization said Monday.
But countries could use emergency measures to get the vaccines out faster if they decide they are needed, Marie-Paule Kieny, director of WHO's Initiative for Vaccine Research, said during a news conference in London, the Associated Press reported.
The problem: The swine flu viruses being used to develop a vaccine are only producing about half as much "yield" to make vaccines as regular flu viruses. So the WHO has asked its network of laboratories to produce a new set of viruses as soon as possible. Before countries can start any large-scale swine flu vaccination campaigns, the vaccines need to be vetted by regulatory authorities for safety issues, the AP reported.
The good news is that the H1N1 swine flu virus is still producing relatively mild cases of infection and most patients recover quickly.
Still, U.S. health officials are very aware that a swine flu vaccination campaign in 1976 was abruptly stopped after hundreds of people reported developing Guillain-Barre syndrome, a paralyzing disorder.
Also Monday, U.S. researchers reported that the H1N1 swine flu virus causes more lung damage than a seasonal flu strain -- at least in some animals. But the virus is still susceptible to antiviral drugs such as Tamiflu.
Reporting in this week's issue of the journal Nature, University of Wisconsin-Madison scientiss Yoshihiro Kawaoka and colleagues took virus samples from patients infected with the H1N1 swine flu and examined their impact on different types of animals. In mice, ferrets and monkeys, infection with the new H1N1 swine flu virus triggered more severe lung disease than a seasonal H1N1 strain.
That may explain why the swine flu has caused some severe cases of pneumonia in otherwise healthy people, the researchers said.
The Wisconsin researchers also said the H1N1 swine flu virus seems to be closely related to the viruses responsible for the deadly 1918-19 Spanish flu pandemic, a finding that has been reported before. Antibodies taken from patients born before 1920 can recognize the H1N1 swine flu virus, but not so for people born after 1920, the scientists said.
But, the researchers added, all antiviral drugs tested, including Tamiflu, were effective in cell cultures against the new virus, lending support to the use of these drugs as a first line of defense.
Last week, U.S. health officials warned against complacency and said the country should be prepared for the swine flu virus' expected return in the fall.
Health and Human Services Secretary Kathleen Sebelius, Department of Homeland Security Secretary Janet Napolitano, Education Secretary Arne Duncan and others led on Thursday an H1N1 swine flu "preparedness summit" at the National Institutes of Health in Bethesda, Md.
"Scientists and public health experts forecast that the impact of H1N1 may well worsen in the fall -- when the regular flu season hits, or even earlier, when schools start to open -- which is only five or six weeks away in some cases," Sebelius said in a news release.
The H1N1 swine flu first surfaced in the United States in mid-April, and has since infected an estimated 1 million Americans or more. Although the virus continues to produce mild illness and patients recover fairly quickly, 211 people in the United States have died from the disease, according to the U.S. Centers for Disease Control and Prevention.
The most recent figures from the World Health Organization put the number of deaths globally at 429.
Health officials are worried that the H1N1 virus could mutate, becoming more virulent and dangerous.
The WHO last month formally declared a pandemic, triggered by the rapid spread of the H1N1 virus across North America, South America, Europe, Australia and regions beyond.
U.S. health officials have said they are considering a swine flu immunization campaign that could involve an unprecedented 600 million doses of vaccine. Still to be worked out is finding enough health-care workers to administer all those shots, and determining ways to record side effects if the vaccine is given at the same time as the seasonal flu vaccine, officials said.
The timing of the program depends on how fast a vaccine can be produced and tested. Preliminary trial vaccines are expected within several weeks, and some vaccine could be available by mid-October, Sebelius said Thursday.
What makes the H1N1 strain different from the typical seasonal flu is that about half of the people killed worldwide were young and previously healthy. In contrast, regular forms of the seasonal flu typically prove most lethal to the very young and the elderly.
To learn more about H1N1 swine flu, visit the U.S. Centers for Disease Control and Prevention.
SOURCES: July 13, 2009, abstract, Nature; July 9, 2009, news release, U.S. Health and Human Services; Associated Press
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